The present invention relates to an address filtering method and unit used in bridge unit or the like for connecting networks.
Relay processing of packets is usually carried out as follows.
A bridge unit comprises an entry table for storing a position at which a terminal is located. In carrying out relaying operation, the bridge unit refers to this entry table and a destination address of an incoming packet to decide whether the packet should be relayed or discarded, that is, the bridge unit carries out address filter processing.
To be more specific, when the destination terminal of the packet is in the a different LAN or when the destination of the packet is not known, the packet is relayed. When the packet is in the incoming direction, it is discarded.
Methods of dynamically learning contents of an entry table have been proposed. For example, a technique described in JP-A-64-39852 is known.
According to this technique, an incoming packet is referred to and its source address and its terminal position are registered in the entry table to carry out learning.
The entry table is reviewed periodically for the purpose of:
1 preventing the table from being filled by the learning; and PA0 2 adjusting to movement of the terminal position, and deleting the registration of a terminal which has not been transmitting or receiving packets from the entry table.